1. Field of the Invention
The present invention relates to an indicator device, such as an industrial (especially manufacturing-industrial) indicator lamp, which guides a light from a light source to a predetermined indicating surface to make an optical indication entirely on the indicating surface, an illuminating device which guides the light from the light source to a light-projected surface to make an illumination entirely on the light-projected surface and an indicator device (LED bulb) consisting of an emitter body with light emitting diode (LED) elements mounted two-dimensionally and a dome-shaped cap member attached thereto.
2. Description of the Background Art
In order for a safe operation of an in-plant system and the like, it is necessary for an operator to always monitor the condition of machinery, facilities and the like while performing operation, control, management and handling over the machinery. For this reason, a control panel and the like in the plant are provided with an indicator lamp to indicate the condition of the system. The indicator lamp has a light-transmissible plate (inscription plate) with characters such as xe2x80x9cONxe2x80x9d, xe2x80x9cOFFxe2x80x9d, xe2x80x9cOPERATIONxe2x80x9d and xe2x80x9cALERTxe2x80x9d, signs, pictures and the like. When the light source behind the inscription plate is turned on according to the operating condition of the system, an optical indication is made entirely on the indicating surface, being visually recognized by the operator. The indicator lamp may be provided in a variety of forms, and among typical forms are a unit indicator lamp for indicating a single information, a collective indicator lamp for indicating plural pieces of information and an illuminated push-button switch with indicator lamp having an additional function of operating the system, such as operation/stop.
In short, the indicator lamp is a device provided on a panel surface of the control panel to inform the operator of the system condition, and assumes a dominant position in a man-machine interface for a safe operation of the system by the operator.
Anyway, there is a request for color-coded representation in such an indicator lamp. Since a control panel and the like usually has a plurality of indicator lamps, if color-coding depending on purposes is made and information (characters, signs, signs and pictures) with coded colors is given, instead of information being monochromatically presented, the viewability of the indicator lamp can be improved.
In the today""s light source available for the indicator lamp, however, the kind of colors of light emitted therefrom is limited and therefore there is a limit of color-coded representation.
Further, it is necessary to prevent the shape of an emitter in the light source (dots of an LED element and filament or bulb of an incandescent bulb) from being externally recognized so that the operator can easily recognize indication such as characters (what are represented by the characters).
Furthermore, a halogen lamp may be used as the light source to achieve a pure-white indicator lamp, but this causes a problem of short lifetime of the light source due to a great amount of heating values, so that it can not be applied to actual use as of today.
If the color of the indicator lamp in an on state (the color of indication light) and the color in an off state (its appearance color) are different, there arises a problem that the color of the indicator lamp in the on state can not be known from the color in the off state. If the color of the indicator lamp in the on state can not be known, especially in a case where a plurality of indicator lamps having plural kinds of colors different from one another are provided in the control panel and the like, it is not easy to recognize what color an indicator lamp in the off state will have in the on state and that makes it difficult to intuitively recognize what the indicator lamp informs with color information.
Though an indication color obtained by transmitting a light from the light source using an incandescent bulb through a milky-white plate has been conventionally called xe2x80x9cwhitexe2x80x9d in this art, the color temperature of the incandescent bulb can not be considered white, being much different from pure white obtained by the light source using a unit of red, green and blue LED elements or the halogen lamp, and the above request is not satisfied.
The present invention is intended to solve the above problems in the prior-art indicator device and an object of the present invention is to provide an indicator device capable of making an optical indication with any colors.
Another object of the present invention is to provide an indicator device which allows high-order achievement in both highly-intensified indication and high diffusibility of light.
A further object of the present invention is to provide an indicator device and an illuminating device capable of eliminating variation in the amount of light on an indicating surface or a light-projected surface.
An yet object of the present invention is to provide an indicator device which achieves any-color indication light from a light emitted by a single-color light source and allows the color of the indicating surface in an on state of the light source (indication light) to be easily recognized from the color of the indicating surface in an off state of the light source with higher productivity and lower cost.
Still another object of the present invention is to provide an indicator device (LED bulb) capable of emitting a light of white or other delicate color which is difficult to emit with a single LED element.
According to the present invention, an indicator device which makes an indication by illuminating a predetermined indicating surface comprises: a light source for emitting a light of a first wavelength; and a fluorescent plate provided between the light source and the indicating surface, for changing at least part of the light of the first wavelength projected thereto from the light source into a light (L2) of a second wavelength longer than the first wavelength and projecting the light of the second wavelength towards the indicating surface.
In the present invention, since the fluorescent plate provided between the light source and the indicating surface changes at least part of the light of the first wavelength projected thereto from the light source into the light of the second wavelength longer than the first wavelength and projects it towards the indicating surface, the color of the light of the second wavelength and the ratio of the light of the second wavelength projected from the fluorescent plate and the light of the first wavelength through the fluorescent plate can be easily changed only by changing the kind of the fluorescent plate to be used, and as a result indication lights of various colors for illuminating the indicating surface can be easily obtained from the single light of the first wavelength. Therefore, since the light source has only to be provided with one kind of light source for emitting the light of the first wavelength, it is possible to ensure higher productivity and lower cost as compared with, for example, a case of changing combination of kinds of the LED elements to be used according to the color of the indication light.
According to the present invention, the indicator device further comprises: a filter provided between the fluorescent plate and the indicating surface, for transmitting at least part of the light projected from the fluorescent plate towards the indicating surface, and in the indicator device, a color of a light through the filter to illuminating the indicating surface in an on state of the light source and an appearance color of the filter which substantially defines a color of the indicating surface in an off state of the light source are substantially identical or similar to each other.
In the present invention, since the light through the filter to illuminate the indicating surface when the light source is on and the appearance color of the filter which defines the color of the indicating surface when the light source is off are substantially identical of similar to each other, the color of the indicating surface in the on state of the light source (in other words, the color of the indication light which makes a lighting of the indicating surface) can be intuitively recognized with ease from the color of the indicating surface in the off state of the light source, and what the surface-illuminated indicator device indicates can be intuitively understood with ease from the color of the indicating surface in the off state.
Further, providing the filter allows only the desired color component (wavelength component) to be extracted among the components of the light emitted from the fluorescent plate, and the color of the light from the fluorescent plate can be thereby changed or corrected easily. As a result, indication lights of various colors can be easily obtained by changing combination of the fluorescent plate and the filter.
According to the present invention, in the indicator device, the fluorescent plate and the filter are united as a wavelength changing member comprising a fluorescent layer having a function of the fluorescent plate and a filter layer having a function of the filter.
In the present invention, since the fluorescent plate and the filter are united as a wavelength changing member comprising the fluorescent layer and the filter layer, the number of parts can be reduced and it is thereby possible to ensure simplification of fabrication process and lower cost.
One indicator device according to the present invention is a surface-illuminated indicator device for making an indication by illuminating a predetermined indicating surface, and the device comprises (a) a light source having a first emitter for emitting the light of the first wavelength and a second emitter for emitting a light of another wavelength different from the first wavelength; and (b) a fluorescent plate having a light-incident surface receiving the light from the light source and a light-outgoing surface facing the indicating surface, for changing part of the light of the first wavelength into the light of the second wavelength longer than the first wavelength.
The above indicator device has a characteristic feature that the color of the light projected from the light-outgoing surface is changeable by changing the emitting condition of the first and second emitters.
As the fluorescent plate, a plate substantially transmitting the light of another wavelength may be used.
On the other hand, another indicator device according the present invention is a surface-illuminated indicator device for making an indication by illuminating a predetermined indicating surface, and the device comprises (a) a light source having a first emitter for emitting the light of the first wavelength and a second emitter for emitting a light of another wavelength different from the first wavelength; and (b) a fluorescent body (wavelength changing member) consisting of a plurality of layered fluorescent plates each having a light-incident surface receiving the light from the light source and a light-outgoing surface facing the indicating surface, for changing part of the light of the first wavelength into a plurality of lights of wavelengths longer than the first wavelength.
The above indicator device has a characteristic feature that the color of the light projected from the light-outgoing surface is changeable by changing the emitting condition of the first and second emitters.
Also in this constitution, as the fluorescent plate, a plate substantially transmitting the light of another wavelength may be used.
In one and another indicator devices according to the present invention, it is preferable to further provide a light diffusion member for diffusing the light on an optical path of the light going from the light source towards the indicating surface, and a hologram diffusion plate may be used as the light diffusion member.
Instead of providing the hologram diffusion plate, a light diffusion material may be mixed into the fluorescent plate.
As an especially-characteristic application of the present invention, the first emitter is a semiconductor light-emitting element which emits a blue light as the light of the first wavelength and the fluorescent plate has the fluorescent characteristics of absorbing part of the blue light emitted from the semiconductor light-emitting element to emit a yellow light as the light of the second wavelength, and it is possible to obtain a substantially white light for the optical indication when only the first emitter is turned on.
A light of a first chromatic color can be projected from the light-outgoing surface when only the first emitter among the light source is turned on, a light of a second chromatic color can be projected from the light-outgoing surface when only the second emitter among the light source is turned on, and a light of a third chromatic color obtained by additive color mixing of the light of the first chromatic color and the light of the second chromatic color can be projected from the light-outgoing surface when both the first and second emitters are turned on.
Further, providing a luminance changing unit for changing luminances of the first and second emitters depending on whether either the first or second emitter is turned on or both the first and second emitters are turned on prevents large variation in luminance of the indication light caused by switching operation of the emitting condition.
According to the present invention, in the indicator device, the light source has the first emitter for emitting the light of the first wavelength and the second emitter for emitting the light of another wavelength different from the first wavelength, and the color of the light projected from the fluorescent plate is changeable by projecting the lights emitted from the first and second emitters into the fluorescent plate and changing the emitting condition of the first and second emitters.